Ion implanters are commonly used in the production of semiconductor workpieces. An ion source is used to create an ion beam, which is then directed toward the workpiece. As the ions strike the workpiece, they dope a particular region of the workpiece. The configuration of doped regions defines their functionality, and through the use of conductive interconnects, these workpieces can be transformed into complex circuits.
As a workpiece is being implanted, it is typically clamped to a chuck. This clamping may be mechanical or electrostatic in nature. This chuck traditionally consists of a plurality of layers. The top layer, also referred to as the dielectric layer, contacts the workpiece, and is made of an electrically insulating or semiconducting material, such as alumina with embedded metal electrodes, since it produces the electrostatic field without creating a short circuit. Methods of creating this electrostatic field are known to those skilled in the art and will not be described herein.
A second layer, also referred to as the base, may be made from an insulating material. To create the required electrostatic force, a plurality of electrodes may be disposed between the dielectric layer and the insulating layer. In another embodiment, the plurality of electrodes may be embedded in the insulating layer. The plurality of electrodes is constructed from an electrically conductive material, such as metal.
FIG. 1 shows a top view of a chuck 10, specifically showing the plurality of electrodes 100a-f of the chuck 10. As shown, each of the electrodes 100a-f is electrically isolated from the others. These electrodes 100a-f may be configured such that opposite electrodes have opposite voltages. For example, electrode 100a may have a positive voltage while electrode 100d may have a negative voltage. These voltages may be DC, or may vary with time to maintain the electrostatic force. For example, as shown in FIG. 1, the voltage applied to each electrode 100a-f may be a bipolar square wave. In the embodiment shown in FIG. 1, three pairs of electrodes are employed. Each pair of electrodes is in electrical communication with a respective power source 110a-c, such that one electrode receives the positive output and the other electrode receives the negative output. Each power source 110a-c generates the same square wave output, in terms of period and amplitude. However, each square wave is phase shifted from those adjacent to it. Thus, as shown in FIG. 1, electrode 100a is powered by square wave A, while electrode 100b is powered by square wave B, which has a phase shift of 120° relative to square wave A. Similarly, square wave C is phase shifted 120° from square wave B. These square waves are shown graphically on the power supplies 110a-c of FIG. 1. Of course, other numbers of electrodes and alternate geometries may be used.
The voltages applied to the electrodes 100a-f serve to create an electrostatic force, which clamps the workpiece to the chuck.
It is difficult to detect arcing or high voltage breakdown conditions occurring at or near the electrostatic chucks. These deleterious conditions may occur with an electrostatic chuck being used with any workpiece processing system, including ion beam line systems and plasma deposition systems. Furthermore, failure sites are typically sufficiently small that they are not easily visible to an operator until the occurrence of a catastrophic failure, during which the chuck, workpieces, or both are damaged.
Consequently, corrective action cannot be taken until the damage has already occurred. This results in lost productivity due to the down time for the processing system, damaged or unusable processed workpieces and a monetary impact resulting from the need to replace the damaged chuck. This results in an increase in the cost of ownership (COO) to the user of an ion implanter or similar systems. Therefore, it would be beneficial if there were a system and method of detecting conditions representative of a future failure absent corrective action sufficiently early so as to avoid damage to the chuck, as well as minimizing lost productivity.